Fetal growth restriction (FGR) increases the risk of offspring developing cardiovascular disease (CVD) in later life. FGR elevates androgen concentrations due to impaired placental androgen metabolism. Androgens function via several known variants of the androgen receptor (AR) to regulate the transcription of genes involved in growth, immune function, and vascular function pathways. Abnormal androgen ligand concentrations or altered AR variant profiles can dysregulate these pathways and contribute to CVD progression in adults. Despite this understanding, it is not known whether the FGR heart has dysregulated androgen signalling in utero. Therefore, we aimed to characterise the androgen signalling axis in the fetal heart in a clinically relevant sheep model of FGR.
Left ventricle tissue was collected from control (female n=5, male n=6) and FGR (female n=5, male n=7) fetuses at 140d gestation (term=150d). AR protein variant expression was quantified using Western blot. A subset of samples (n=4/sex/group) were used for RNA-seq: differential gene expression analysis was performed using the DESeq2 package, and pre-ranked gene set analysis was performed using GSEA v4.1.0.
Full-length AR (AR-FL) cytosolic and nuclear expression did not change between groups or sexes. Cytosolic expression of the antagonistic AR variant, AR-45, was increased in male FGR compared with male controls (P=0.0002), whereas nuclear AR-45 expression did not change between groups or sexes. The nuclear AR-FL/AR-45 ratio was increased in FGR, irrespective of sex (P=0.0186), whereas the cytosolic AR-FL/AR-45 ratio was reduced in male FGR compared with male controls (P=0.0147). In both sexes, the androgen response gene set was upregulated in FGR compared with sex-matched controls.
Dysregulated androgen signalling in the FGR heart may be due to an imbalance between the AR-FL/AR-45 ratio. Targeting aberrant cardiac androgen signalling in utero may reduce the incidence of CVD in FGR offspring.